In Japanese Patent Laid-Open No. 2008-74127 (a patent document 1), an airbag ECU is disclosed as a collision determination apparatus for determining a vehicle collision.
In patent document 1, a main sensor and a safe sensor are described as sensors for providing a collision determination signal. The main sensor is disposed as a G-sensor on a side portion of a vehicle for detecting a right-left direction of acceleration, and the safe sensor is disposed as a G sensor at a center of the vehicle for also detecting the right-left direction of acceleration. The collision determination apparatus uses a redundant circuit system by including a main control circuit and a sub-control circuit. The main control circuit determines a collision based on the output signal from the main sensor and the safe sensor, i.e., the signal from each of G sensors in various positions, and the sub-control circuit determines a collision based on the output signal from the main sensor.
An airbag ECU, which is equipped with a side-collision determination function, may be expected to be capable of performing a collision determination by using various types of sensors. For instance, in a side collision in which the vehicle is impacted by a colliding object on its side, a pressure sensor that detects a steep change of an in-door pressure may be used. Alternatively, an impact sensor that detects an acceleration from an impact of the collision in which the in-door pressure is measured as an air pressure of a space inside of a door may also be used. By having a pressure sensor in an in-door space, the side collision at a door portion can be accurately detected based on the steep change of the air pressure of the in-door space that is caused by a sudden depression of a door outer panel.
However, the airbag ECU of patent document 1 uses a single type of sensor, i.e., the G sensors only. The combined use of various sensor types, such as a combined use of the G sensor and the pressure sensor, is not expected by the airbag ECU.
Further, when different types of sensors are combined, respective determination logics for accommodating the different types of sensors are stored in the integrated circuits, such as an application specific integrated circuit (ASIC). However, one ASIC targeted to one combination of sensors in one vehicle type may not be used for a different combination of sensors, because the ASIC is not rewritable. That is, in a different type of vehicle, a sensor combination may be different, due to the variation of the installation positions and/or the variation of the sensor types. Therefore, one ASIC made for one vehicle type is not compatibly used in other vehicle types. Accordingly, the versatility of the ASIC is very low, and requires a specific ASIC for a specific vehicle type.